1. Field of the Invention
The present invention relates to a fuel cell system for purging water and the like within an anode loop by air and the like.
2. Description of the Related Art
Generally, a fuel cell is configured by comparting a cathode at one side and an anode at the other side with sandwiching a proton conductive polymer electrolyte membrane (PEM) and generates power by an electrochemical reaction of oxygen in the air supplied to the cathode and hydrogen supplied to the anode. And in such a fuel cell system with such the fuel cell, if because water is produced by the electrochemical reaction of oxygen and hydrogen, the fuel cell is stopped in a state that the water stays within the system as it is and long time lapses from a power generation stop, there is a possibility that the water freezes in winter and a cold district.
As a technology for such the problem is conventionally known one that purges water and the like remaining within a cathode loop and an anode loop by branching air sent out of a compressor and supplying it within the cathode loop and the anode loop in a stop of a fuel cell system (see paragraphs 0022 to 0024 and FIG. 1 of Japanese Patent Laid-Open Publication No. 2003-331893). Meanwhile, in a description below a process of purging water and the like within the anode loop by a gas such as air other than a hydrogen gas is referred to as “anode sweeping process.”
However, the conventional technology performs the anode sweeping process just after there occurs a stop request for stopping a fuel cell system, and therefore, when a pressure within the anode loop becomes a comparatively higher state (state of a comparatively many hydrogen gas remaining) than an atmospheric pressure in the stop of the fuel cell system, there is a possibility that a hydrogen gas and air for sweeping react within the same loop, and in this case there is a possibility that a membrane of the fuel cell is deteriorated.
Consequently, a fuel cell system is strongly requested that can prevent a deterioration of a membrane accompanied with the anode sweeping process.